Background and Objectives:The endoscopic transsphenoidal approach (TSA) is the standardized surgical approach to sella lesions providing a wider field and resulting in fewer neurosurgical complications. However, sinonasal complications are relatively less studied. This study aims to analyze sinonasal morbidities after endoscopic TSA performed by a single center. Materials and Methods: Among 154 patients who underwent endoscopic TSA from 2015 to 2022, 107 patients who were followed up for more than 3 months were included and retrospectively reviewed. Sinonasal complications including crust, discharge, septal perforation, synechia and polypoid sphenoid mucosa at postoperative 3 month were evaluated with olfactory function. The patients were subdivided into nasoseptal flap (NSF), non-NSF, 1st phase (initial 3 years, n=53) and 2nd phase (later 4 years, n=54) groups for further analysis. Results: There were 47 male (43.9%) with a mean age of 51.6 (range 15-83). The mean follow-up duration was 10.9 (range 3-46) months. Crust (28, 26.2%) was the most frequent morbidity followed by synechia (18, 16.8%), hyposmia (17, 15.9%), discharge (14, 13.1%), polypoid sphenoid mucosa and septal perforation (8, 7.5%). NSF was associated with crust formation and septal perforation (p<0.001). Olfactory function was relatively preserved at 3 month (p=0.065). Postoperative cerebrospinal fluid (CSF) leak decreased in the 2nd phase (4/54, 7.4%) compared to the 1st phase (12/53, 22.6%) (p<0.05). Conclusion: Crust was the most frequent sinonasal morbidity after endoscopic TSA followed by synechia. NSF was associated with crust and septal perforation. Post-op CSF leaks could be reduced after overcoming the learning curve of endoscopic TSA.